Coastal Paleontologist Blogs on Early Seal Evolution

29 03 2010
This image is courtesy of Wikimedia Commons.  It is by Vivien Thiessen, and is licensed under the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.

The comparative anatomy of an otariid seal and a phocid seal, both of which are discussed in Coastal Paleontologist’s blog piece.

The Coastal Paleontologist has a very interesting piece on early seal evolution.  It can be found at the following location:  Pinniped ancestry: the “Oligocene Seal” from South Carolina.

Following is the first paragraph from the blog, just as a teaser:

One of the most fascinating aspects of the study of marine mammals are the origins of the land to sea transition in various groups. Often marine mammals are so adapted for marine existence, that it is difficult to identify what group (fossil or modern) they descended from. Such has been the case with the origin of whales, for example. While I’m certainly interested in cetaceans, there has been a ton written about them, and I’m currently more intrigued by pinnipeds.





Tyrannosaur a Whole Genus of Critters

28 03 2010
 
 
 
 
This image is courtesy of Wikimedia Commons.  It is by stu_spivack, and is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.

At 12 feet long, this juvenile T. rex, known as Jane, which is on exhibit at Burpee Museum of Natural History in Rockford, IL, USA, is just slightly larger than the new Tyrannosaur recently discovered in Australia.

Tyrannosaurs are more than just the single species Tyrannosaurus rex, though that’s the one most people think about.  Tyrannosaurus is a genus, the next taxonomic order above a species, and consists of more than 30 species of dinosaur.  These species fall into the group of dinosaurs known as theropods, and lived during the late Jurassic and throughout the Cretaceous periods.  Tyrannosaurus rex is the most famous member of the genus, and the biggest physically.  It is also one of the latest, living during the last three- to four-million years of the Cretaceous, right up to the end of the age of dinosaurs.

 The number of Tyrannosaur fossils discovered to date has been so great (e.g., more than 30 skeletons of T. Rex, alone), that it has allowed scientists to study them as much or more than any other type of dinosaur.

Tyrannosaurs were bipedal carnivores, having long, heavy tails, relatively tiny (though very strong) front arms, and massive skulls.  While other theropod dinosaurs equaled or exceeded T. rex in size, it was the largest known tyrannosaurid and one of the largest known land predators of its day, measuring up to 12.8 meters (42 ft.) in length, 4 meters (13 ft.) tall at the hips, and weighing as much as 6.8 metric tons.

While definitely a carnivore, scientists have long debated whether T. rex was an apex predator or a scavenger.  The debate is one of the longest running arguments in all of paleontology.

The genus was widespread through the northern hemisphere, but until very recently was unknown from the southern one.  In March, 2010, scientists from Monash University in Melbourne, Australia, reported the discovery of a tyrannosaurid hip bone from Dinosaur Cove in southern Victoria, Australia.  This appears to be a smaller animal than T. rex, and likely a new species.

Researchers estimate that the animal was approximately three meters long and weighed about 80 kg.  As such, it would have been similar to, though slightly larger than a human.  It lived about 110 million years ago.

The following are a few of the Tyrannosaurus species that have been identified, who described them, and when they were described:

  • Tyrannosaurus amplus (Marsh, 1892)
  • Tyrannosaurus bataar (Maleev, 1955)
  • Tyrannosaurus lanpingensis (Yeh, 1975)
  • Tyrannosaurus luanchuanensis (Dong, 1979)
  • Tyrannosaurus rex (Osborn, 1905)
  • Tyrannosaurus turpanensis (Zhai, Zheng, and Tong, 1978)




Call for Abstracts

27 03 2010

The 3rd Annual Meeting of the Southeastern Association of Vertebrate Paleontology will be held at the South Carolina State Museum, Columbia, SC, from June 2 – 4, 2010.

We invite student, professional and avocational paleontologists to submit abstracts for proposed presentations on any topic related to Vertebrate Paleontology.

In your submission please include the following information in this order:

  1. Name, institution, mailing address, telephone number and email for you and your co-presenters.
  2. Title of presentation.
  3. Abstract (please limit to 300 words; avoid citations and illustrations).
  4. Indicate any special AV needs.
  5. Indicate one of the following selections:
    1. Oral presentation only
    2. Oral and poster presentations
    3. Poster presentation only

Both a PC with PowerPoint and a Macintosh with PowerPoint will be available.

Email submissions as a Microsoft Word attachment to James L. Knight at:
jim.knight@scmuseum.org

Abstracts must be submitted for consideration no later than May 1, 2010.





Energy Expenditure and Body Composition in Two Sympatric Lemurs does NOT Support Theories Accounting for Unusual Socio-Ecological Traits and Life History Features

27 03 2010
This image is from Wikimedia Commons and is in the Public Domain

Lemur Catta, also known as the Ring-tailed Lemur

In an article published March 25, in the Online journal PLoS one, researchers present evidence showing no support for the theory that energy conservation behaviors and mechanisms are the result of evolutionary adaptation in response to unusual socio-ecological traits and life history features of those species.

Following is the abstract from the article.  For the complete article, please see the following URL:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0009860.

Abstract

Background

Evolutionary theories that account for the unusual socio-ecological traits and life history features of group-living prosimians, compared with other primates, predict behavioral and physiological mechanisms to conserve energy. Low energy output and possible fattening mechanisms are expected, as either an adaptive response to drastic seasonal fluctuations of food supplies in Madagascar, or persisting traits from previously nocturnal hypometabolic ancestors. Free ranging ring-tailed lemurs (Lemur catta) and brown lemurs (Eulemur sp.) of southern Madagascar have different socio-ecological characteristics which allow a test of these theories: Both gregarious primates have a phytophagous diet but different circadian activity rhythms, degree of arboreality, social systems, and slightly different body size.

Methodology and Results

Daily total energy expenditure and body composition were measured in the field with the doubly labeled water procedure. High body fat content was observed at the end of the rainy season, which supports the notion that individuals need to attain a sufficient physical condition prior to the long dry season. However, ring-tailed lemurs exhibited lower water flux rates and energy expenditure than brown lemurs after controlling for body mass differences. The difference was interpreted to reflect higher efficiency for coping with seasonally low quality foods and water scarcity. Daily energy expenditure of both species was much less than the field metabolic rates predicted by various scaling relationships found across mammals.

Discussion

We argue that low energy output in these species is mainly accounted for by low basal metabolic rate and reflects adaptation to harsh, unpredictable environments. The absence of observed sex differences in body weight, fat content, and daily energy expenditure converge with earlier investigations of physical activity levels in ring-tailed lemurs to suggest the absence of a relationship between energy constraints and the evolution of female dominance over males among lemurs. Nevertheless, additional seasonal data are required to provide a definitive conclusion.





Scientist Shows Post-Mating Pre-Fertilization Barrier to Cross Species Breeding

25 03 2010

Daniel R. Matute of the department of ecology and evolution at the University of Chicago has published a study of two species of Drosophila, that show, for as far as I am aware the first time, the presence of postmating prezygotic isolation.  Specifically, that means a barrier or barriers that act after mating but before fertilization.

The paper appeared on March 23, in the online journal Public Library of Science (PLoS) Biology.  It is important from an evolutionary standpoint as a demonstration of the diversity of ways that reinforcement by gametic isolation can bolster isolation between species or proto-species.

Following is the abstract from the paper.  For the complete paper, please see the following URL:  http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1000341.

Abstract

Reinforcement, a process by which natural selection increases reproductive isolation between populations, has been suggested to be an important force in the formation of new species. However, all existing cases of reinforcement involve an increase in mate discrimination between species. Here, I report the first case of reinforcement of postmating prezygotic isolation (i.e., barriers that act after mating but before fertilization) in animals. On the slopes of the African island of São Tomé, Drosophila yakuba and its endemic sister species D. santomea hybridize within a well-demarcated hybrid zone. I find that D. yakuba females from within this zone, but not from outside it, show an increase in gametic isolation from males of D. santomea, an apparent result of natural selection acting to reduce maladaptive hybridization between species. To determine whether such a barrier could evolve under laboratory conditions, I exposed D. yakuba lines derived from allopatric populations to experimental sympatry with D. santomea, and found that both behavioral and gametic isolation become stronger after only four generations. Reinforcement thus appears to be the best explanation for the heightened gametic isolation seen in sympatry. This appears to be the first example in animals in which natural selection has promoted the evolution of stronger interspecific genetic barriers that act after mating but before fertilization. This suggests that many other genetic barriers between species have been increased by natural selection but have been overlooked because they are difficult to study.





Researchers Use DNA to Find New Human Species… Probably

24 03 2010

In a report published Wednesday in the journal Nature, Russian scientists report using mitochondrial DNA (mtDNA) to identify a new species.  While the identification is tentative, and awaits confirmation, it none-the-less represents an important new use of DNA technology.

The discovery occurred in the summer of 2008, when the scientists were digging in Denisova cave, in Siberia.  They were looking for the remains and artifacts of Neanderthals, who occupied the cave between 30,000 and 48,000 years ago.  During excavations, they found a small sliver of finger bone.  According to the scientists, it was considered unremarkable at the time.

However, when they sent it to German scientists to have the DNA extracted and sequenced, they were in for a surprise.  The results did not match Neanderthals.  Nor did it match modern humans, who were also living in the area at the time.

The conclusion was that the bone represented a here-to-fore unknown human species.  Based on the differences between the bone’s DNA and that of modern humans, it is estimated that the species diverged from human ancestors a million years ago, long before the split between modern humans and Neanderthals.  By inference, this means that the proposed species left Africa in a previously unknown migration, sometime between that of Homo erectus about 1.9 million years ago and that of the Neanderthal ancestor Homo heidelbergensis, 300,000 to 500,000 years ago.

But, as yet, none of this is entirely certain.  The use of mtDNA poses its own problems, and scientists also must examine the bone’s nuclear DNA to get a full picture.  While mtDNA comes through the mother’s lineage, nuclear DNA comes from through the father’s.  It is important to have both in order to make a proper assessment.

Researchers point out that it is possible that some modern humans or Neanderthals living in Siberia 40,000 years ago had unusual mtDNA.  Only by also examining the nuclear DNA will a complete enough picture of the person it belonged to come out, allowing scientists to make a determination.  Such a picture might also allow scientists to properly define this new relative’s position within the human family tree.

To read more about this find, please see the article in Nature News at the following URL:  http://www.nature.com/news/2010/100324/full/464472a.html.





Findings Provide Strongest Link Yet to Volcanically-Associated Cause for End-Permian Mass Extinction

24 03 2010
This image was created by Kiff and is courtesy of Wikimedia Commons.  It is licensed under the GNU Free Documentation License.

Pangea as scientists believe it appeared at the end of the Permian Period

Research results published Monday in the online journal Proceedings of the National Academy of Sciences (PNAS) provides the strongest association between the mass extinction that occurred at the end of the Permian period and volcanic eruptions (specifically those occurring along the east coast of the United States during the beginning of the breakup of Pangea.

 The authors were Jessica H. Whiteside, Paul E. Olsen, Timothy Eglinton, Michael E. Brookfield, and Raymond N. Sambrotto.

 Following is the abstract for the article

 Abstract

A leading hypothesis explaining Phanerozoic mass extinctions and associated carbon isotopic anomalies is the emission of greenhouse, other gases, and aerosols caused by eruptions of continental flood basalt provinces. However, the necessary serial relationship between these eruptions, isotopic excursions, and extinctions has never been tested in geological sections preserving all three records. The end-Triassic extinction (ETE) at 201.4 Ma is among the largest of these extinctions and is tied to a large negative carbon isotope excursion, reflecting perturbations of the carbon cycle including a transient increase in CO. The cause of the ETE has been inferred to be the eruption of the giant Central Atlantic magmatic province (CAMP). Here, we show that carbon isotopes of leaf wax derived lipids (-alkanes), wood, and total organic carbon from two orbitally paced lacustrine sections interbedded with the CAMP in eastern North America show similar excursions to those seen in the mostly marine St. Audrie’s Bay section in England. Based on these results, the ETE began synchronously in marine and terrestrial environments slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco, a CO super greenhouse, and marine biocalcification crisis. Because the temporal relationship between CAMP eruptions, mass extinction, and the carbon isotopic excursions are shown in the same place, this is the strongest case for a volcanic cause of a mass extinction to date.

For more information, please see the original PNAS journal article at the following URL:
http://www.pnas.org/content/early/2010/03/15/1001706107.full.pdf+html?sid=9cdfecda-f033-4211-958c-db9fdb86a405.

This image is in the public domain because it contains material originally created by the U.S. Geological Survey.

This animation shows the breakup of Pangea, that began at the end of the Permian Period. Volcanic Activity associated with this breakup (particularly in Siberia and the US east coast) is believed to have triggered the largest mass extinction in earth's history.